Dental Malocclusion Types Quiz

Anterior Ratio and Overall Ratio

• Anterior Ratio is calculated by dividing the sum of mesiodistal width of mandibular anterior teeth (3-3) by the sum of mesiodistal width of maxillary anterior teeth (3-3) and multiplying by 100.
• Average value of Anterior Ratio is 77.2 (range: 75.55-78.85).
• Overall Ratio is calculated by dividing the sum of mesiodistal widths of 12 mandibular teeth (6-6) by the sum of mesiodistal widths of 12 maxillary teeth (6-6) and multiplying by 100.
• Average value of Overall Ratio is 91.3 (range: 89.39-93.21).

Tooth Dimension Discrepancy

• Tooth dimension discrepancy is calculated by comparing the values found according to the formulas with the values in Bolton's standard table.
• If the tooth size discrepancy is less than 1.5 mm, it is insignificant.
• Larger values create treatment problems.

Consequences of Bolton Ratio

• If the Bolton ratio is high in the upper jaw:
  • With Angle Class I closure in the first molars, an overjet will occur in the anterior region.
  • With Angle Class I closure in the first molars and no overjet, crowding will occur in the upper teeth.
  • With Angle Class I closure in the first molars and no overjet and crowding, diastema will occur in the lower tooth arch.
  • With no diastema in the lower arch, no crowding in the upper arch, and normal overjet, the posterior bite will shift to Angle Class III.
• If the Bolton ratio is high in the lower jaw:
  • With Angle Class I closure in the first molars, head-to-head or crossbite will occur in the lower anterior region.

Arch Length Deviation

• Arch Length Deviation (ALD) = Available arch length - Required arch length.
• If ALD is negative, space is needed in the arch (crowding).
• If ALD is positive, there is excess space in the arch (diastema).

Space Analysis in Mixed Dentition

• Three approaches to calculate the mesiodistal dimension of unerupted permanent teeth:
  • Measuring tooth dimension on radiographs.
  • Estimation from Proportion Tables.
  • Other methods (not specified).

Measurement on Radiographs

• Measure tooth width on periapical X-ray film.
• Magnification ratio is calculated by comparing the mesiodistal size of a tooth in the model and in the X-ray.

Estimation from Proportion Tables

• Tables are used to estimate the mesiodistal dimensions of unerupted canines and premolars based on the sum of the mesiodistal widths of the lower incisors (incisor amount).

Hays-Nance Analysis Method

• Required Arch Length is calculated by measuring and summing the mesiodistal width of each permanent tooth mesial to the first permanent molars.
• Available Arch Length is calculated by two methods: yellow wire method and measurement with a Boley caliper.
• Dental arch is divided into four segments for measurement.